Glass powder, especially biologically active glass powder, and method for producing glass powder, especially biologically active glass powder

ABSTRACT

The invention relates to glass powder, especially a biologically active glass powder, which includes a plurality of glass particles and which is characterized by the following features: the glass particles are made up by &gt;90% of non-spherical particles; the geometry of the individual non-spherical particle is characterized by a ratio of length to diameter of 1.1 to 10 5 .

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to glass powder, especially biologically activeglass powder, and a method to produce glass powder, especiallybiologically active glass powder.

2. Description of the Related Art

Biologically active glass powders in the form of bio-active glasspowders are already known from U.S. Pat. No. 5,074,916 and in the formof anti-microbial active glass powders from WO 03/018499. The glasspowders include a plurality of glass particles of any shape includingspherical as well as non-spherical particles, for example in the form ofglass fibers. The production of particles of this type may occur indifferent methods, whereby the glass is generally melted and convertedto a semi-finished state or to ribbons which are then ground to acertain granular size. It has been demonstrated that the biologicaleffectiveness is greatly dependent upon the particle size whichmanifests in an accordingly high degree of grinding.

Methods for producing particles from a melt, especially from a mineralor glass melt are known in a plurality of implementations. For example,in one of the methods for the production of glass wool for insulatingpurposes which is described in documentation EP 13 60 152 and EP 09 31027 the glass melt is put into a rotating drum which is equipped withsmall diameter holes that are located in the wall which forms thesurface area. Due to the centrifugal forces the glass melt is forcedthrough the small holes. A significant disadvantage associated with theuse of rotating elements of this type is that they are subjected toespecially high wear and tear in the hot area due to the necessarilyhigh rotational speed, thereby providing only a relatively low life spanof such units.

A method for producing metallic glass powders is already known from U.S.Pat. No. 4,386,896. In this method, the glass melt is atomized under theinfluence of moving elements and a gas and is directed toward acentrifuge disk. The described atomizing methods include a singlesubstance nozzle as well as the use of cold gas. Also in this scenariothe mechanical elements of the apparatus which are necessary for theatomization are also exposed to the high temperatures of the glass melt,resulting in high maintenance of this type of apparatus. In addition,the throughput is determined by the speed of the motion and therotational speed of the rotating elements.

A method for atomizing of metal melts which utilizes two nozzles in theatomization area is described in WO 98/12116. Here, a first nozzle unitis utilized for atomizing and a second nozzle for providing the cold gasin order to cool the created droplets. In contrast, DE 100 02 394 C1discloses a method for the atomization of melts utilizing hot gas inorder to produce spherical particles. Here, a melt having a dynamicviscosity η in the range between 0.01 and 100 Ns/m² is produced. Themolten stream is atomized utilizing a primary gas, whereby the primarygas has a temperature of at least T_(A)=T_(G)

T_(G)=Glass forming temperature

T_(A)=Glass exit temperature

at the nozzle discharge point. Cooling of the particles which wereformed during atomizing occurs in a cooling zone downstream from thenozzle in the production flow through utilization of a quenching medium,whereby the temperature of the quenching medium is lower than thetemperature of the glass forming temperature. In this method the glassmelt stream is led over a certain distance and the primary gas issupplied through several individual nozzles. This supply method over along period of time avoids cooling and favors the formation of sphericalparticles. Particles of this type however, do not fulfill the demandsput upon biologically active glasses which must be characterized by ahigh biological effectiveness.

What is needed in the art is to develop a glass powder, especially abiologically highly active glass powder, as well as a method to producea glass powder, especially a biologically highly active glass powderwhich is characterized by a high throughput combined with low thermaland mechanical demand upon the elements which are associated with theparticle formation, as well as by a favorable energy balance. Theconstruction and controls related expenditure should be kept as low aspossible.

SUMMARY OF THE INVENTION

The inventors recognized that the biological effectiveness is determinedprimarily by the particle size, especially by the surface that isavailable for reactions. The inventive biologically active glass powderincludes a plurality of non-spherical glass particles. The share of thenon-spherical glass particles relative to a predetermined total volumeof particles is preferably higher than 70%, preferably higher than 80%.The geometry of the individual non-spherical particle is provided by aratio of length to diameter of 1.1 to 10⁵, preferably 100 to 10⁴,especially preferably of 10 to 10⁴.

The described particle geometry provides a substantial surfaceenlargement of a predefined amount of glass powder, especiallybiologically active glass powder when compared with the same amount ofglass powder having spherical particles, resulting especially in theavailability of a larger effective reactive surface for biologicalprocesses and reactions.

The length of the individual glass particle is approximately 1 μm to 10⁵μm, preferably 10 μm to 10⁴ μm, especially preferably 100 μm to 10⁴ μm.

Fibers are characterized by a diameter in the range of 0.5 μm to 10 μm,preferably 0.5 μm to 2 μm.

Bio-active as well as antimicrobial glass powders are sub-summarizedunder biologically active glass powders. In the case of bioactive glasspowders the glass of the glass powder includes the following components:

SiO₂ 40-70 weight % P₂O₅ 2-15 weight % Na₂O 0-35 weight % CaO 5-35weight % MgO 0-15 weight % F 0-10 weight %

Bioactive glass differs from conventional lime-sodium-silicate glassesin that it is not rejected by the body. The designation “bioactive”describes a glass which forms a firm connection with body tissue,thereby forming a hydroxyl-apatite layer. These types of glass powdersdisplay a biocidal or biostatic effect vis-à-vis bacteria, fungi andviruses. In contact with humans they are skin tolerant, toxicologicallyharmless.

In a biologically active glass powder in the form of an antimicrobialactive glass powder the glass of the glass powder includes the followingcomponents:

P₂O₅ 0-80 weight % SO₃ 0-40 weight % B₂O₃ 0-50 weight % Al₂O₃ 0-10weight % SiO₂ 0-10 weight % Li₂O 0-25 weight % Na₂O 0-20 weight % K₂O0-25 weight % CaO 0-25 weight % MgO 0-15 weight % SrO 0-15 weight % BaO0-15 weight % ZnO 0-25 weight % Ag₂O 0-5 weight % CuO 0-10 weight % GeO₂0-10 weight % TeO₂ 0-15 weight % Cr₂O₃ 0-10 weight % J 0-10 weight %wherebyThe sum SiO₂+P₂O₅+B₂O₃+Al₂O₃ amounts to between 30-80 weight %and the sumZnO+Ag₂O+CuO+GeO₂+TeO₂+Cr₂O₃+J amounts to 0.1-40 weight %and the sumR¹ ₂O+R²O amounts to 0.1-60% weight whereby R¹ is an alkali metal and R²is an earthalkali metal.

In the case of antimicrobial glasses, especially glass powders fromantimicrobial glasses, alkalis of the glass are exchanged with H+−ionsof the aqueous medium due to reactions on the surface of the glasspowder. The antimicrobial action of the ion exchange is based, amongother factors, on an increase of the pH value and the osmotic effectupon micro-organisms. Based on increased pH value due to ion exchangebetween one metal ion, for example an alkali or earth alkali metal ionand the H⁺ ions of the aqueous solution, as well as due to anion-contingent limitation of cell growth (osmotic pressure, interruptionof metabolic processes of the cells) glass powders of this type reactantimicrobial in aqueous mediums.

With all the previously listed glass powders Na₂O is utilized as afluxing agent during melting of the glass. At concentrations <5%, themelting characteristics are influenced negatively. In addition, thenecessary mechanism of the ion exchange is no longer sufficient toachieve the antimicrobial effect.

Alkali and earth alkali oxides may especially be added in order toincrease the ion exchange, thereby intensifying the antimicrobialeffect. The amount of Al₂O₃ which may be added to enhance the chemicalconstancy of the crystallization stability as well as the control of theantimicrobial effect is max 10 weight %.

B₂O₃ functions as a network creator and may also aid the control of theantimicrobial effect.

ZnO is an essential component for hot-forming characteristics of theglass. It improves the crystallization stabilities and increases thesurface tension. In addition, it can support the antimicrobial effect.Low SiO₂ contents increase the crystallization stability. In order toachieve an antimicrobial effect as much as 25 weight % should becontained.

In accordance with the current invention the method for producing glasspowder, especially biologically active glass powder includingnon-spherical particles can be sub-divided essentially into twocategories. In a first method a glass melt (which can also be referredto as a melt, a molten mass or a molten glass mass) is produced,followed by the particle formation or fiber formation. Methods areselected for the particle formation which distinguish themselves througha low constructive and manufacturing expenditure and which especiallyassure a high throughput at a favorable energy balance. According to afirst design the particle formation occurs through granulation from themelt. This occurs due to an intense shear effect upon the free-flowingglass stream and appropriate cooling. The granules which are created bythis granulation are characterized by a large size and therefore a smallsurface. Particles having a diameter of 0.5 μm to 10 μm and a length of2 to 10⁵ μm are created. Shaping may be fiber like as well as irregular.Granulation can be followed by a grinding process. In the process ofthis the particles are reduced to a size of 0.5 to 8 μm diameter and alength of 2 to 100 μm. Irregularly formed particles which as a rule arenot formed spherically, result again from the also irregularly formedparticles.

In accordance with an especially advantageous design form the formationof the glass particles fundamental to the grinding process occursthrough an atomizing process. This ensures that predominantlynon-spherical particles, especially fibers, are available as startingmaterial for the subsequent grinding process. The still hot glass melt,preferably at a temperature of between 1400-1800K is being atomized byway of a gas whereby atomizing occurs preferably directly from thedischarge nozzle at the discharge or transfer area of the melting zoneto the atomizing zone. Two nozzles are essentially utilized for theatomization, whereby the first nozzle serves to direct the glass meltwhile the second nozzle initiates the actual atomization process.Through synchronization of the individual process parameters with eachother the final structure can be extensively influenced, especially theparticle geometry which is already available for the optional grindingprocess. In order to operate at a high throughput the atomization of theglass melt occurs at a high temperature. Consequently the glass melt issupplied to the atomizing area at a low viscosity. In addition theatomizing process is established largely by the process parameters inthe atomizing zone which are determined by the temperature of thesupplied glass and the prevailing pressure conditions. Any inert or drygases can be used as atomizing gas. Preferred is dry nitrogen.

A gas having a low temperature, especially cold gas at a temperature of70K to 600K, preferably 200K to 500K, especially preferably 250-400K ispreferably utilized as atomizing gas. The cold gas on the one hand has acooling effect on the glass melt, thereby providing it with a higherlevel of viscosity.

At the same time shear forces are transferred to the glass through thegas resulting in irregularly formed particles, especially fibers.

The atomization process can also feasibly be accomplished throughatomizing by way of hot gas. In this scenario the gas is then suppliedat a temperature of between 500 and 1300K, preferably 700 to 1230K. Apressure of between 0.2 and 0.5, preferably 0.34 MPa is applied in theatomization zone.

The atomization process then occurs preferably in the area of entry ofthe glass melt into the atomization area. Atomization occurs preferablyby way of a nozzle arrangement which provides a planiform effect uponthe molten stream whereby the atomization area is kept relatively shortin order to achieve quick cooling while creating irregularly formedparticles. Cooling can occur directly through the supply of anappropriate gas or quenching medium or indirectly, that is without theactive influence of additional measures.

Particle sizes, especially lengths of 2-100 μm can be achieved in thesubsequent grinding process. Particle sizes of 2-10 μm have proven to beespecially advantageous. The grinding process itself may be conducteddry or also with the assistance of aqueous or non-aqueous grindingmedia.

The inventive method utilizes preferably a hot gas atomizationarrangement. This includes a melting apparatus representing a meltingzone, as well as an atomization apparatus representing the atomizationzone, whereby the melting apparatus is connected with the atomizationapparatus. The atomization apparatus includes two nozzles which areallocated to the glass melt, especially to the glass melt stream andthrough which a gaseous medium acts upon the glass melt stream. Theglass melt stream itself is preferably delivered through an openingwhich is preferably located in the direction of gravitation, or througha nozzle, into the atomization zone of the atomization apparatus. Theatomization zone can be sub-divided into two sections—a first sectionwhere the glass melt, especially the glass melt jet being emitted fromthe opening or the nozzle is still directed in the direction ofgravitation, and a second section which is characterized by the effectof the gaseous medium which is used for atomizing upon the glass meltjet. In this arrangement a first nozzle for the inlet of a gaseousmedium is allocated to the discharge nozzle in order to direct themolten jet. This is preferably in the embodiment of an annular gap andis located coaxially to the discharge opening of the first nozzle.Arrangements which are equipped with a plurality of individual nozzleswhich are located symmetrically around the circumference of the moltenjet are also feasible. The second nozzle is designed such that thegaseous medium impinges upon the molten jet at an angle, whereby anangle range of between 20° and 60°, preferably of 40 to 60°, especiallypreferably of 45° is selected. The second nozzle is designed so that theimpingement occurs planiform or linear uniformly in circumferentialdirection, specific to the surface of the molten jet and also withoutinterruptions. With regard to the direction of discharge the firstnozzle is located parallel to molten glass jet. The second jet islocated downstream from the first jet and is aligned at an angle to saidfirst jet. Atomization occurs preferably in an area of the emission fromthe discharge opening, that is the discharge nozzle and therefore in theinitial area of the atomization zone. Due to the then occurring coolingparticles having an irregular geometry are formed, preferably in fiberform. In addition these can be further cooled in a downstream coolingdevice. As a rule the particles which were formed in the atomizationzone are further transported over a distance of approx. 1 m and are onlythen subjected to a cooling process. This can be in the form of a liquidbath or through the addition of an inflowing gaseous medium.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIGS. 1 a-1 c show signal flow diagrams which illustrate inschematically simplified depiction the basic sequence of the inventiveprocess;

FIG. 2 shows a schematically simplified depiction of a hot gas atomizingapparatus which illustrates inventive implementations of the methodaccording to FIG. 1 c;

FIGS. 3 a-3 c show a schematically simplified depiction of the viscositycharacteristics of the melt relative to the temperature of the melt forvarious glass compositions;

FIG. 4 shows a schematically simplified depiction of the inventiveprocess for producing particles in a gravity-type atomizer;

FIGS. 5 a-5 c illustrate the resulting fibers according to theindividual design examples according to Table 1 with the assistance ofRem-pictures (scanning electron microscope picture); and

FIG. 6 illustrates the change of the resulting fiber diameters duringcold gas atomization at various melting temperatures.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate embodiments of the invention, and such exemplifications arenot to be construed as limiting the scope of the invention in anymanner.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more particularly to FIGS. 1 a-1 c,there is shown signal flow diagrams which illustrate in schematicallysimplified depiction the basic principle of the inventive method toproduce non-spherical glass particles, especially from biologicallyactive glass. The biologically active glasses include the so-calledbioactive glasses which are characterized by the following glasscomposition ranges:

SiO₂ 40-70 weight % P₂O₅ 2-15 weight % Na₂O 0-35 weight % CaO 5-35weight % MgO 0-15 weight % F 0-10 weight %as well as antimicrobial glasses which are characterized by thefollowing glass composition:

P₂O₅ 0-80 weight % SO₃ 0-40 weight % B₂O₃ 0-50 weight % Al₂O₃ 0-10weight % SiO₂ 0-10 weight % Li₂O 0-25 weight % Na₂O 0-20 weight % K₂O0-25 weight % CaO 0-25 weight % MgO 0-15 weight % SrO 0-15 weight % BaO0-15 weight % ZnO 0-25 weight % Ag2O 0-5 weight % CuO 0-10 weight % GeO₂0-10 weight % TeO₂ 0-15 weight % Cr₂O₃ 0-10 weight % J 0-10 weight %wherebySiO₂+P₂O₅+B₂O₃+Al₂O₃ is between 30-80 weight %and the sumZnO+Ag₂O+CuO+GeO₂+TeO₂+Cr₂O₃+J is between 0.1-40 weight %andR₂O+RO is between 0.1-60% weight whereby R is an alkali metal or anearth alkali metal.

In the case of antimicrobial glasses, especially glass powders fromantimicrobial glasses, alkalis of the glass are exchanged with H+−ionsof the aqueous medium due to reactions on the surface of the glasspowder. The antimicrobial action of the ion exchange is based, amongother factors, on an increase of the pH value and the osmotic effectupon micro-organisms.

In a first process step the glass is subjected to a melting process. Inthis process a glass melt having a high temperature, preferably in therange of 1400 to 1800K, especially preferably 1800K is produced. In thesecond process step the particle formation or fiber formation occurs.This can be followed by a third process step which is a grindingprocess. This is however not imperative. Already, the particle formationprocess in the second process step which occurs for example throughgranulation/fiber production due to shear effects from the free flowingglass stream, and appropriate cooling produces particles having adiameter of 0.5 μm-10 μm and a length of 2-10⁵ μm. Said particlesalready possess a surface structure large enough that they can be usedas biologically highly active glass without having to undergo anadditional grinding process. A grinding process following the particleformation process essentially permits non-spherical particles of acertain size in the range of 0.5 μm-8 μm and a length of 2-100 μm to beproduced. Specific to a predefined volume of starting glass a shareof >90% of non-spherical particles is strived for. Non-sphericalparticles are understood to be all achievable geometric shapes,preferably fibers, however, with the exception of spherical particles.Particle formation may occur in various ways.

According to FIG. 1 b the particle formation occurs generally throughgranulation from the melt. The process includes quick cooling of aliquid glass melt in a water bath or a gas, allowing solid materialgranules to be formed. These solid material granules are then subjectedto a grinding process. The particles formed in this process may vary. Onthe one hand, they may be spherical particles, or on the other handnon-spherical particles, whereby however in both instances thenon-spherical particles are produced by the optional subsequent grindingprocess.

An especially preferred option to produce almost exclusivelynon-spherical particles is illustrated in FIG. 1 c in a schematicsummarization of the process steps. This particle formation processincludes atomization or pulverization by use of gas. Depending upon theconfiguration, a cooling process for the particles which were producedduring atomization may be implemented prior to the grinding process. Thenon-spherical particles which are available following the grindingprocess are characterized by a larger active surface at the identicalglass volume when compared with the spherical particles. This translatesfor example, to a greater biological effectiveness.

FIG. 2 illustrates one implementation of a method according to FIG. 1 c,whereby the particle formation occurs essentially through pulverizationor atomization. Here, two nozzles located in tandem in the direction ofthe melt stream flow are utilized. Said nozzles direct the gas flows sothat a return of the melt is avoided. In this scenario the melt streamis directed by the gas flowing from the first nozzle and is atomized bythe gas which flows from the second successive nozzle. The two processsteps—producing the melt and particle formation—are realized in a hotgas atomizing apparatus 1. With regard to the implementation of theindividual process steps said apparatus is sectioned into differentzones which are characterized by the individual devices implementingthis function. In this example the hot gas atomization apparatus 1includes one melting zone 2, one atomization zone 3 as well as onecooling zone 4 which, in a preferred embodiment is also followed by aseparation zone 5. A melting apparatus 6 is provided in the melting zone2. This generally includes a device 7—a receptacle for glass—in theembodiment of a pot or a trough. This device 7 is assigned to a heatingdevice 8 which may, for example, be in the embodiment of an inductionheater or an induction furnace. In this context the glass is heated inthe melting apparatus 6. Due to the temperature increase said glassbecomes soft and the viscosity is reduced. Examples of the temperaturedependency of the glass viscosity are given in FIGS. 3 a through 3 c forvarious glass compositions according to Table 2 of this application.FIG. 3 a illustrates the viscosity-/temperature characteristic for aglass composition according to design example 1 in Table 2. This isidentified with the reference number 100. The viscosity-/temperaturecharacteristic for a glass composition according to design example 2 inTable 2 is identified with the reference number 110.

FIG. 3 b illustrates the viscosity-/temperature characteristic for aglass composition according to design example 4 in Table 2. This isidentified with the reference number 120.

FIG. 3 c illustrates the viscosity-/temperature characteristic for aglass composition according to design example 7 in Table 2. This isidentified with the reference number 130. It is apparent that theviscosity is reduced with increasing temperature of the glass melt 9(which can also be referred to as a melt, a molten mass, or a moltenglass mass) which results from the heating process of the biologicallyactive glass. The glass melt 9 then comes into the atomizing apparatus10 which forms the atomizing zone 3. There may be variations in theconfiguration of the atomizing apparatus 10 depending on how the glassmelt 9 is directed. This applies particularly to the configuration andespecially to the orientation and the geometry of the discharge nozzle11 for the glass melt and the nozzles 12 and 13 which direct the gasflows which influence the glass melt 9. In accordance with the inventiontwo nozzles are provided which affect the glass melt in this instancenozzles 12 and 13. With the atomizing zone 3 oriented in the directionof gravity these are located following each other in down streamdirection of the glass melt flow. The second nozzle 13 which is known asthe so-called secondary nozzle serves to atomize the glass melt 9 whilethe gas flow through the nozzle 12 which is located prior to said secondnozzle is utilized to prevent a return of the droplets or fibers whichwere created by the atomization into the atomization zone and to preventwetting and clogging of the discharge or atomizer nozzle 11 and of theguide devices located upstream from it. The atomizer apparatus 10 isconnected with the melting apparatus 6 via a guide device 14 whichincludes preferably a so-called Pt-guide tube which is located at thebottom end of the pot or trough and which discharges into the atomizernozzle. The gas to influence the glass melt 9 in the atomizing zone 3 isprovided by a gas supply unit 15. Preferably this unit includes a gaspre-heating device 16, especially a propane gas burner to which the gaswhich is to be heated is supplied. The gas pre-heating device 16 isconnected with a gas tank 17 which is indicated only schematically inthe drawing and which contains the gas which is to be heated, wherebythe pre-heating device 16 is also connected with the atomizer apparatus10. Inert gases are used as atomizing gases, for example nitrogen. Thegas is blown into the melt, especially the glass melt 9, thus leading toatomization. The specific design and arrangement of the atomizing zone 3is illustrated in an example of a gravity arrangement in FIG. 4. Bothnozzles 12, 13 for the primary gas, in other words for the gas that iseffective in the atomizing zone 3 are shown. The particle stream whichis formed downstream from the nozzle 13 then reaches the cooling zone 4.A second gas and/or water is utilized as a quenching medium. The secondgas may be a liquefied gas. The quenching medium can be blown in againstthe direction of the particle stream flow, in the direction of nozzle13. It is however also possible to add the quenching medium fordirecting the particle stream in the direction of flow or at an angle.

Additional nozzles are provided to blow in the quenching medium. A bathconsisting of liquefied gas or water can also be provided as quenchingmedium. The particles from the atomizing zone 3 then drop into thecooling zone 4 and are subsequently removed. Particles which are movedalong by the gas flow are separated from the gas flow in a separator 18in the embodiment of a cyclone separator. As an option the herebyproduced particles may be supplied to a grinding device which isillustrated here only as a black box 19. The relevant particles are thensubjected again to a mechanical process so that particles having adiameter of 0.5-10 μm and a length of 2-100 μm are created.

FIG. 4 again schematically illustrates the function of the atomizerapparatus 10 in the embodiment of a gravity atomizer 20 by depicting asegment of the illustration in FIG. 2 of the hot gas atomizer apparatus1. Clearly shown is the discharge nozzle 11 which is preferably in theembodiment of a concentric nozzle and from which the glass melt 9 isexpelled in gravity direction. The gas supply device 15 is connectedwith said nozzle whereby the gas emerging from this device exits throughan annular gap 21 which is configured coaxially to the nozzle 11 wherethe glass melt jet is released and which approximately surrounds saidnozzle in circumferential direction. The annular gap 21 is located inthe area of the discharge opening or discharge nozzle 11 which releasesthe glass melt 9. This first nozzle 12 which is formed by the annulargap 21 is designed such that the gas jet discharges through this nozzle12 parallel to the glass melt stream 9. In this configuration the gascan flow over the entire circumferential direction in the annular gap orat least over a section. It is however critical that a guiding functionfor the glass melt 9 is achieved through the gas which is directed viathe first nozzle 12. The glass melt stream 9 which is herewith directedin vertical direction is then subjected to the gas flow of the secondnozzle 13. This nozzle is configured such that the gas discharges at anangle of approx. 20-60°, preferably approximately 45° in the directiontoward the glass melt 9, especially the melt jet. This melt jet is beingatomized through the influence of the gas which is ejected through thesecond nozzle 13 and which is preferably also supplied through the gassupply device 15. It is preferred if the same gas is always supplied tothe first and the second nozzle 12, 13. The atomizing effect is therebyessentially determined by the emission speed of the melt stream 9 or themelt jet from the discharge nozzle 11, as well as by the configurationof the nozzle 13, especially the speed, the utilized gas, as well as thepressure in the atomizing zone 3.

The gas supplied through the nozzles 12 and 13 can be the same gas, orit may consist of various gas mixtures. Preferably however, the same gasis always used. In addition it is also feasible with the inventiveutilization of the hot gas atomizer apparatus to facilitate the hot gasatomization at a gas temperature of more than 1000K, preferably 1273K atan admission pressure of 0.1 to 6 MPa. At room temperature a gas speedof approximately 180 m/s occurs as a rule in the atomizing zone 3 at anadmission pressure of 0.55 Mpa, while this can reach up to 250 m/s at1073 K. In accordance with an especially advantageous arrangement theglass melt is brought to a maximum temperature of 1800 K in the meltingdevice whereby due to gravity it then flows through the so-calledplatinum guide tube to the atomizer nozzle 11. According to one designexample the inside diameter of this guide tube measures preferably 5 mm.The melt then drops into the atomizing zone 3 and is atomized by the gasflow of the second nozzle 13. In addition to providing directivefunction the gas flow of the first nozzle 12 is used to prevent returnof droplets or fibers into the atomizing zone 3 and in addition to avoidwetting and clogging of the guide tube and the atomizer nozzle 11. Thepressure in the first nozzle 12 is kept at 0.15-0.2 Megapascal. Thetemperature of the atomizing gas is adjustable. Droplets or fibers whichare created by atomization are transported approximately 1 m in thespray tower and are subsequently cooled by appropriate ways as alreadydescribed—cold gas or spray water. The resulting particles are removed.Particles from the gas flow are then transported with the gas flow intothe cyclone 18 where they are discharged. In order to achieve thegreatest possible number was well as fine fibers it has beendemonstrated that the temperature of the glass melt 9 must be as high aspossible already at the time of the particle formation, while thetemperature in the atomizing area can then be very low and that theassociated prevailing pressures are manageable. Table 1 belowillustrates examples of variations of the individual process parametersfor the utilization of the hot gas atomizer apparatus 1, whereby theindividual variations 1 through 5 are consecutively numbered while thetemperature of the glass melt 9, as well as the temperature of the gaswhich is to be supplied through the nozzles 12 and 13, and the pressurein the atomization zone 3 have been varied.

TABLE 1 Process Parameters of trials Temperature Atomizing Gas, Trial ofN₂ Pressure Quenching Run # Melt Temperature, K MPa Water, l/h 1 1673753 0.34 50 2 1673 1223 0.34 100 3 1473 293 0.4 0 4 1573 293 0.4 0 51743 293 0.4 0

FIG. 5 a shows an REM picture of the fibers from a method with theprocess parameters from experiment 3. FIG. 5 b shows the REM picture ofthe fibers from variation 4, and FIG. 5 c shows the REM picture of thefibers with variations of the process parameters according to experiment5. It can be seen that the fiber diameter reduces considerably withvarying melting temperatures during cold gas atomization as illustratedin the trials 4 and 5 which in turn leads to a finer breakdown andbetter fiber formation and thereby larger surface formation. The resultof this is that atomization of a glass melt at very high temperature ofsame and thereby very low viscosity with cold gas is selected as anespecially preferred method for particle formation. This offers theadditional advantage that the cooling effect can be considerablyreduced. Especially quenching in a water bath results partially in thatcooling can largely be dispensed with.

Examples of possible compositions for biologically active glass powderswith essentially non-spherical particles are given in Table 2, below,without however being limited to these (“Eg.” in Table 2 means“example”).

TABLE 2 Glass Compositions: Composition Eg. Eg. Eg. Eg. Eg. Eg. Eg. Eg.Eg. Eg. Eg. Eg. (weight %) 1 2 3 4 5 6 7 8 9 10 11 12 SiO2 45.00 63.4061.00 4.00 35.00 Na2O 24.50 11.90 5.80 6.60 12.50 29.50 6.60 6.50 14.60Li2O 1.60 1.60 1.60 K2O 7.40 7.40 7.40 CaO 24.50 11.90 1.00 3.00 7.5029.50 1.00 2.00 3.30 MgO 15.00 P2O5 6.00 66.90 65.90 31.70 69.00 66.306.00 31.70 31.70 33.50 B2O3 29.80 37.00 Al2O3 6.20 6.20 6.00 6.20 SO318.50 18.50 15.10 Ag2O 1.00 2.00 2.00 1.00 SO3 18.50 TiO2 1.00 ZnO 15.0016.00 33.20 7.50 32.20 32.30 33.50 Sum 100.00 100.00 100.00 100.00100.00 100.00 100.00 100.00 100.00 100.00 100.00 Consistency 2.79892.204 3.0733 2.7349 (g/cm3) Alpha (20° C.; 12.71 4.48 17.29 4.03 8.3912.83 300° C.)(1e−6/K) Tg (° C.) 521 352 466 253 387 538 369 253 265 390VA (TEMP at 811 562 953 419 1177 592 1248 350 373 1e4 dPas)(° C.) Tempat 1e7.6 432 319 463 dPas (° C.) Temp at 1e13 354 257 382 dPas (° C.)Tg—VA 290 210 487 166 790 223 97 108

While this invention has been described with respect to at least oneembodiment, the present invention can be further modified within thespirit and scope of this disclosure. This application is thereforeintended to cover any variations, uses, or adaptations of the inventionusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this invention pertains andwhich fall within the limits of the appended claims.

Component Identification  1 Hot gas atomizer apparatus  2 Melting zone 3 Atomizing zone  4 Cooling zone  5 Separation zone  6 Melting device 7 Receptacle for the biologically active glass  8 Heating device  9Glass melt 10 Atomizer device 11 Discharge nozzle 12 Nozzle 13 Nozzle 14Guiding device 15 Gas supply device 16 Device to pre-heat the gas 17 Gastank 18 Separation device 19 Grinding device 20 Gravity atomizer 21Annular gap

1. A method to produce biologically active glass powder comprising thefollowing steps: producing a glass melt from a predefined volume ofglass; forming a plurality of particles from said glass melt byatomizing, said plurality of particles including a plurality ofnon-spherical particles individual ones of which have a ratio of lengthto diameter of 1.1 to 10⁵, the biologically active glass powderincluding a higher than 90% content of said plurality of non-sphericalparticles, a particle geometry of said plurality of particles beinginfluenced by synchronization of a first plurality of processparameters, said atomizing being established by a second plurality ofprocess parameters in an atomization zone determined by a temperature ofa supplied gas and a plurality of prevailing pressure conditions;atomizing said glass melt in an atomizer apparatus to which said glassmelt is supplied and which includes a first nozzle device and a secondnozzle device which are located in tandem in a flow direction of saidglass melt stream of said glass melt, at least one primary gas flowbeing admitted using said first nozzle device which discharges parallelto said glass melt stream in an area of entry of said glass melt streaminto said atomizer apparatus and which guides said glass melt stream, asecond gas flow being admitted for atomizing using a second nozzledevice at an angle upon said glass melt stream, said second gas flowbeing admitted uniformly in a circumferential direction of said glassmelt using said second nozzle device; heating a gas which is to besupplied through said first and said second nozzle devices to atemperature of between 293 and 1300K; and admitting said gas which is tobe supplied through said first and said second nozzle devices into saidatomizer apparatus at a pressure of between 0.1 and 0.6 MPa.
 2. Themethod in accordance with claim 1, wherein said glass melt is producedfrom said predefined volume of glass with one of a first composition anda second composition, said first composition including: SiO₂ 40-70weight % P₂O₅ 2-15 weight % Na₂O 0-35 weight % CaO 5-35 weight % MgO0-15 weight % F 0-10 weight %,

said second composition including: P₂O₅ 0-80 weight % SO₃ 0-40 weight %B₂O₃ 0-50 weight % Al₂O₃ 0-10 weight % SiO₂ 0-10 weight % Li₂O 0-25weight % Na₂O 0-20 weight % K₂O 0-25 weight % CaO 0-25 weight % MgO 0-15weight % SrO 0-15 weight % BaO 0-15 weight % ZnO 0-25 weight % Ag₂O 0-5weight % CuO 0-10 weight % GeO₂ 0-10 weight % TeO₂ 0-15 weight % Cr₂O₃0-10 weight % J 0-10 weight %,

wherein in said second composition a sum SiO₂+P₂O₅+B₂O₃+Al₂O₃ amounts tobetween 30-80 weight %, a sum ZnO+Ag₂O+CuO+GeO₂+TeO₂+Cr₂O₃+J amounts to0.1-40 weight %, and a sum R¹ ₂O+R²O amounts to 0.1-60% weight, R¹ beingan alkali metal, and R² being an earth alkali metal.
 3. The method inaccordance with claim 1, wherein subsequent to said heating andadmitting steps, said plurality of particles are ground to more than 90%non-spherical particles with a particle size having a ratio of length todiameter which is 1.1 to 10⁵.
 4. The method in accordance with claim 1,wherein subsequent to said heating and admitting steps, said pluralityof particles are ground to more than 90% non-spherical particles with aparticle size having a ratio of length to diameter which is 100 to 10⁴.5. The method in accordance with claim 1, wherein subsequent to saidheating and admitting steps, said plurality of particles are ground tomore than 90% non-spherical particles with a particle size having aratio of length to diameter which is 10 to 10⁴.
 6. The method inaccordance with claim 1, wherein said glass melt is heated to atemperature of between 1400 and 1800 K.
 7. The method in accordance withclaim 1, wherein said glass melt is heated to a temperature of between1600 and 1800 K.
 8. The method in accordance with claim 1, wherein saidsecond gas flow is admitted at an angle of between 20 to 60°.
 9. Themethod in accordance with claim 1, wherein said first and said secondnozzle devices are supplied with said gas having a same third pluralityof process parameters.
 10. The method in accordance with claim 1,wherein said gas which is to be supplied through said first and saidsecond nozzle devices is an inert gas.
 11. The method in accordance withclaim 1, further comprising the step of quenching in a cooling zone saidplurality of particles which are formed from said glass melt.
 12. Themethod in accordance with claim 11, wherein said quenching occursthrough admitting one of a gas and a bath.
 13. The method in accordancewith claim 1, wherein said atomizer apparatus is a hot gas atomizerapparatus.
 14. The method in accordance with claim 1, further comprisingthe step of grinding said plurality of particles which are formed fromsaid glass melt, said grinding occurring with a medium.
 15. The methodin accordance with claim 1, wherein individual ones of said plurality ofnon-spherical particles have a length of 1 μm to 10⁵ μm and a diameterin a range of 0.5 μm to 10 μm.
 16. The method in accordance with claim1, wherein individual ones of said plurality of non-spherical particleshave a length of 1 μm to 10⁵ μm and a diameter in a range of 0.5 μm to 2μm.
 17. The method in accordance with claim 1, wherein individual onesof said plurality of non-spherical particles have a length of 10 μm to10⁴ μm and a diameter in a range of 0.5 μm to 10 μm.
 18. The method inaccordance with claim 1, wherein individual ones of said plurality ofnon-spherical particles have a length of 10 μm to 10⁴ μm and a diameterin a range 0.5 μm to 2 μm.
 19. The method in accordance with claim 1,wherein individual ones of said plurality of non-spherical particleshave a length of 100 μm to 10⁴ μm and a diameter in a range of 0.5 μm to10 μm.
 20. The method in accordance with claim 1, wherein individualones of said plurality of non-spherical particles have a length of 100μm to 10⁴ μm and a diameter in a range of 0.5 μm to 2 μm.